Process for removing ammonia and hydrogen sulphide from gases



F. OVERDICK July 26, 1932.

PROCESS FOR REMOVING AMMONIA AND HYDROGEN SULPHIDE FROM GASES Filed July 6, 1931 SWWfMMQ/fmu rnrrz ovnnmcx, nnNrNDUs'rarn man@ July 28,1932

UNITED STATES PATE-Nr oFFlcE AKTIENGESELLSGHAFT,

PROCESS FOR Application July 6, 1931,

The present invention is an improvement in and further development of U. S. Patent 1,826,779 (Serial No. 286,712, filed June 19, 1928,) for the removal of ammonia and hydrogen sulphide from gases by means of polythionate and thiosulphate so l sists in effecting regeneration of the used .y ofthe stream of solution washing solution by divertingonly a portion from the washing stage in which an excess of phide over the ammonia is present and 1n utilizing the liquor returning'fromthe regeneration first for washing the gas which is free from ammonla in order to convert the liquor to the free sulphurous acid and then after further use in the last washing stage returning the washing stage first mentloned with the result that part of the washing solution goes through a cycle between the 1nammonia are available.

dividual gas washers andthe regeneration..

By appropriately adjusting the circulation serving for the solution the thiosulphate and polythionate portions of the solution in the regeneration can be brought to the ratio desired for the further working upv of the excess solution.

U. S. Patent (Serial No. 286,712, iiled June 19, 1928) describes a process wherein ammonia and hydrogen sulphide are washed out from gases by means of polythionate solutions and indeed in such a manner that the ammonia is removed romthe gas wholly or in part before the washing process and the as is then treated in several stage's'with polythionate solution, the ammonia which has been separated being added inthe last stage. In the first washing stages such a quantity of hydrogen sulphide is separated that in the last stage for each molecule of hydrogen sulphide atleast two molecules of By taking up ammonia and hydrogen sulphide polythionate which in turn is by treatment is converted to thiosulphate, regenerated to polythionate with sulphurous acid.

BEHOVING AMMONIA AN D HYDBOGN SULPHIDE Serial No.

utions and con-f hydrogen sul-v OF LEVERKUSEN/WINDOW, GEBIANY, .ABSIGN-OB T0 I. Garn- OF IBANKFOBT-ON-THE-IAIN, G

non casas 549,011, ma m Germany my 1o, 1930.

The regenerated solution always contains noticeable quantities of free sulphurous acid, which on again being Aused for the treatment of the gas combines ,with ammonia. to form sulphite with monia islost so far as absorption of the hydrogen sulphide is concerned. Furthermore, it is known that the regeneration process is interferred with when the liquor to be regenerated; such as last washing stage still contains free ammonia, since the ammonium bisulphite formed strongl retards the polythionate formation (see unke, Gas andvWasser 1925, page 4:20, right hand column).

In accordance with the present invention all these drawbacks are obvlated very simply by proceeding as follows: f.

Only part of the gas washing Yliquor is caused to iow continuously to the regeneration. The part4 of the solution `returning from the re eneration and still containing free acid is rst treated in a washing stage, in which the gas contains hydrogen sulphide but no ammonia. The free sulphurous thereuponA reacts in the known manner w1 part of the hydrogen sulphide with the result Y that the solution leaving the washer is practically free from sulphur dioxide and on entering Y sumes ammonia. The part of the'solution issuing from the last stage and still containing free ammonia serves for the reliminary treatment of the gas in a specia y inse washer, an excess of hydrogen the quantity of ammonia being herealwa s present, withV the result that the part of t e Y solution returning to the regeneratitntlan us cannot lead to interference ini nate formation. Accordingly between the absorption stages and the regeneration there circulates therefore in the manner descrl a slow partial stream the strength whereof the result that part of the amu that withdrawn from the u acid 70V the last washing stage no longer con- 75 sulphide over 80 he poiythio- 88 ammonia is separated from the gas -containers BI, Bn, B

solution, containing Y tion of which is towards dioxide and d eo F ditions. A further advantage of this manner of worln'ng is to be found in the fact that it is possible to adjust the circulation and the addition of sulphur dioxide in there eneration stage to comply with the ratio o thiosulphate: polythionate to 2:1 withY the result that the excess-liquor continuously Howing out can be boiled without special treatment to form sulphate and sulphur:

smnnzsos.

e Obviously any other desired ratio of thiosulphate: olythionate can of course be maintained wit out special dilhculty.

he improved process is illustrated by the attached drawing.

e drawing illustrates example, as coke factor the process, for applied to the purification of gas by the semi-direct man- `ng, in which only part of the coolers l and 2 with the water of condensation and after separation from tar in 3 tar passing to 4) and concentration in ammonia still 8 to wh the ich it passes from the reservoir 7, being raised by the lifting pump 6 from the tank 5, is led into the washer III ofthe olythionate process. After the cool` ing an separation of tar. from the remainder I, II and III.

are irrigated with the solutions from the corres onding the washer I contains only a portion of the ammonia and almost the ole quantity of hyd result that in hydrogen sulprincipally thiosulphate besides a little polythionate, is led from this washing stage tothe container Bw, the soluregenerated in the washer R by treatment with gases containing sulphur dioxide.

An equal quantity of freshly regenerated solution Hows onfrom BW Yto t e'container rB11-and here serves for the washing of the ammonia free gas in washer II.` In this sta e t eV free sulphur dioxide always present 1n the regenerated solution reacts with the hydrogen sulphide of the gas with the result that the portion of the solution flowing on m is practically rom Bm part o and polythionate in the ratio'desired for boil- 1ng the solution. Y Y

Y and he gas passing into Y Laeaaea Thereaction ,taking place in the Various n parts of the plant are illustrated by the following equatlons: n

i r (NHJSlOw (NH.) 2s=2 un0 2szoses n i n the first washing of h stages in which ydrogen sulphid an EXCESS e over the ammonia` is roo presentand in washing with-the liquor returning from the regeneration rstly the gas which 1s free from ammonia in order to con- In testimony whereof, I a my signature.

FRITZ OVERDICK.

'K im@ free from sulphur limi 

